Şenay Katırcıoğlu

Structural and electronic properties of bare and hydrogenated silicon clusters

We have investigated the structural and electronic properties of both bare and hydrogenated Sim (m=5,17,29,35,47) clusters using density functional theory. It has been found that the total binding energy decreases as the cluster size increases for both bare and hydrogenated silicon clusters. Moreover, optimization contracts the clusters; optimized geometry of bare clusters is quite different from those of hydrogenated clusters. The electronic structure calculations give the size-dependent band gap for the hydrogenated silicon clusters and the band gap increases as the cluster size decreases.

Density functional theory calculations of small ZnmSn clusters

Abstract We have investigated the structural and electronic properties of isolated neutral ZnmSn clusters for m+n≤4 by performing density functional theory calculations at B3LYP level. We have obtained the optimum geometries, the electronic structures, and the possible dissociation channels of the clusters considered.

Decomposition of C60 molecules on Si(111) surface

We have investigated the adsorption and decomposition of C60 molecules on a Si(111) surface at elevated temperatures by using a molecular-dynamics computer simulation. The potential energy function used in the calculations includes both two- and three-body interactions, which are represented by Lennord-Jones and Axilrod-Teller potentials, respectively. The abrupt decomposition of C60 molecules on a Si(111) surface is obtained at 910 K.

Adsorption of water on stepped Si(100) surface

Abstract We have investigated possible water forms on stepped Si(100) surface. Calculations are performed by using the empirical tight-binding method. Two types of adsorption model of water on stepped Si(100) surface have been considered; one of them is the dissociative type (H, OH) and the other is the molecular type (H 2 O). The results of the density of states supported by total electronic energy calculations indicate a dissociative type of water adsorption on the stepped Si(100) surface.

DISSOCIATION OF PH3 AND AsH3 ON Ge(100)(2x1) SURFACE

The most stable structures for the dissociation of phosphine and arsine on Ge(100)(2x1) surface have been investigated by relative total energy calculations based on Density Functional Theory. It has been found that the thermodynamically preferred structures in the dissociation path of phosphine and arsine are the same; PH2 and AsH2 products prefer to be on a single Ge dimer bond, but PH and AsH prefer to be between the adjacent Ge dimers. According to the optimization calculations, the dissociation path started with the adsorption of PH3(AsH3) on the electron deficient side of the Ge dimer bond is ended with the formation of P–P (As–As) dimers parallel to the dimers of Ge.

Structure and stability of GenCm−n clusters

Abstract Density functional theory method has been used to predict the structural and energetic properties of Ge n C m − n ( n =1, m =3–14; n =2, m =4–15) isomers. The optimized stable structures have been found to be linear(chain) for all Ge n C m − n ( n =1, m =3–9; n =2, m =4–10) clusters and planar(ring) for all Ge n C m −1 ( n =1, m =10–14; n =2, m =11–15) isomers. It has been also found that the Ge n C m − n ( n =1, m =3–14; n =2, m =4–15) clusters with odd m are more stable than those with even m .

Structural and electronic properties of InmSen microclusters: density functional theory calculations

Abstract We have investigated the structural and electronic properties of isolated In m Se n microclusters for m + n ≤4 by performing density functional theory calculations. We have obtained the optimum geometries, possible dissociation channels and the electronic structure of the clusters considered.

First-principles calculations for the structural and electronic properties of GaAs1−xPx nanowires

Structural stability and electronic properties of GaAs1−xPx (0.0≤x≤1.0) nanowires (NWs) in zinc-blende (ZB) (∼5≤ diameter ≤∼21A) and wurtzite (WZ) (∼5≤diameter≤∼29A) phases are investigated by first-principles calculations based on density functional theory (DFT). GaAs (x=0.0) and GaP (x=1.0) compound NWs in WZ phase are found energetically more stable than in ZB structural ones. In the case of GaAs1−xPx alloy NWs, the energetically favorable phase is found size and composition dependent. All the presented NWs have semiconductor characteristics. The quantum size effect is clearly demonstrated for all GaAs1−xPx (0.0≤x≤1.0) NWs. The band gaps of ZB and WZ structural GaAs compound NWs with ∼10≤ diameter ≤∼21A and ∼5≤diameter≤∼29A, respectively are enlarged by the addition of concentrations of phosphorus for obtaining GaAs1−xPx NWs proportional to the x values around 0.25, 0.50 and 0.75.

DECOMPOSITION OF C60 MOLECULES ON Si(100)(2 × 1) SURFACE

We have investigated the decomposition of C60 molecules with low and high coverages on Si(100)(2×1) surface at elevated temperatures. We also investigated the decomposition of an isolated C60 molecule. We employed molecular-dynamics simulation using a model potential. It has been found that C60 decomposes on Si(100) surface after 1000 K in the case of low coverage (0.11), however in high coverage case (0.67), C60 molecules decompose after 900 K. On the other hand, isolated C60 molecule decomposes after 7500 K, interestingly it shows a phase change from 3D to 2D at higher temperatures.

Dependence of energy levels and optical transitions on layer thicknesses in InSe/GaSe superlattices

We have investigated the dependence of energy levels and optical transition matrix elements in InSe/GaSe superlattices on well and/or barrier widths. Self-consistent-field calculations have been performed within the effective-mass theory approximation.